In recent years, the presence of dust that has harmful effects on the human body when a human breathes it in has become a social problem. Such dust includes various substances, for example, suspended particulate matter such as fine particulate matter (PM2.5), asbestos known as a substance that causes lung cancer, silica, carbon nanotube, and anticancer drugs. At a site to study and analyze these hazardous particles, these substances are handled at high concentrations for long periods of time, so that researchers and operators are in an environment with a higher risk of being exposed to these hazardous substances.
In particular, with a mass concentration measurement of PM2.5, there is a need to attach a filter to a prescribed collection device installed in the atmosphere, and measure the weight of particulate matter collected by this filter. At this time, for stable measurement by preventing adsorption of particulate matter due to moisture absorption of the filter, there are standards strictly limiting a measuring environment to a temperature of 21.5±1.5° C., humidity of 35±5%, and scale accuracy of ±1 μg. Therefore, a space in which a scale is installed must be controlled so that the temperature and humidity fall within the standards.
FIG. 9 is a schematic view of a scale chamber realizing constant temperature and constant humidity, conventionally used for measuring hazardous particles such as PM2.5. Reference sign 1 denotes a main body of a temperature and humidity control device, reference sign 2 denotes an indoor equipment of a temperature and humidity control device, reference sign 3 denotes a work space, reference sign 4 denotes a heat-insulated chamber covering the scale chamber, and reference sign 5 denotes a scale. The arrow shows airflow. That is, after the scale chamber is insulated and the work space 3 is changed into a uniform environment by generating air blow whose temperature and humidity are managed by the temperature and humidity control devices 1 and 2, measuring is performed.
However, this environment creation has a problem in which, there is a need for considerable capital investment, and a measured value of the scale 5 becomes unstable due to strong air blow for agitating air inside a room sufficiently large for a person to enter. A further problem is that hazardous particles are disturbed by the air blow and scatter in the work space 3, and an operator becomes exposed to the hazardous particles.
On the other hand, as systems that prevent exposure to hazardous particles, a glove box (for example, refer to Patent literature 1) by which hazardous substances are contained in an enclosed space and handled via gloves, and a draft chamber (for example, refer to Patent literature 2) that forcibly exhausts air from a work space and forcibly suctions the hazardous substances to prevent it from flowing outside, are known.